In a photomechanical process, to improve the reproduction of continuous gradation with a dot image or the reproduction of line images, it is necessary to obtain photographic characteristics of super high contrast (particularly having a gamma value of not less than 10). For this purpose, a method using a combination of a light-sensitive material comprising a silver chloride emulsion or a silver chlorobromide emulsion having a high silver chloride content and a hydroquinone developer (infectious developer) wherein the effective concentration of sulfite ions is markedly decreased, usually to not more than 0.1 mol/l, has usually been employed. This method using such infectious developers (lith developers), however, has a problem in that the developer is seriously unstable and cannot be stored for more than 3 days because the sulfite ion concentration of the developer is low.
As an improved method for obtaining photographic characteristics of super high contrast using a stable developer, a method using specific hydrazine derivatives as described in U.S. Pat. No. 4,224,401 is known. In accordance with this method, a high concentration of sulfite ions is allowed to exist in the developer and thus the developer is protected against air oxidation, leading to an increase in the stability thereof.
U.S. Pat. No. 4,269,929 discloses an improved method over the above super high contrast image-forming method using hydrazine derivatives, in which in order to obtain a negative image having a high gamma value, a developer having a lower pH value is used, and amine compounds are added to the developer.
In this method, when compounds having a low molecular weight among acylhydrazine derivatives are dissolved in the developer, the compounds exert adverse influences on other light-sensitive materials, particularly light-sensitive materials for rapid access, and thereby cause an increase in fog. It is therefore preferred to use acylhydrazine derivatives having a ballast group to provide diffusion resistance to make them difficult to be dissolved in the processing solution. With such diffusion resistance type of hydrazines, however, photographic characteristics of high sensitivity and high contrast are often difficult to obtain. In order to obtain such characteristics, it is necessary for the hydrazines to be added in a large amount. In addition, a problem arises in that with a solution in which the activity has been decreased as a result of processing a large number of light-sensitive materials, the sensitivity and gradation .gamma. are decreased.
It has been found that to overcome the above problems, it is effective to use compounds having a diffusion resistant group among acylhydrazine derivatives having a urea connecting group. However, a light-sensitive material using such hydrazine derivatives has problems in that the sensitivity and gradation are decreased when the material is stored for a long period of time, particularly under high temperature and humidity conditions.
Thus a system in which the above problems of a light-sensitive material using acylhydrazine derivatives, i.e., reductions in sensitivity and gamma value resulting from the processing using a low activity developer deteriorating the processing solution and the long term storage, have been overcome has been strongly desired.